Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of TiO2.
Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of TiO2.
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DOI：
10.1021/jp0469618
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发表时间：
2005-01
期刊：
影响因子：
--
通讯作者：
B. Xin;L. Jing;Z. Ren;Baiqi Wang;H. Fu
中科院分区：
文献类型：
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作者：
B. Xin;L. Jing;Z. Ren;Baiqi Wang;H. Fu
采用溶胶-凝胶法在无光条件下制备了不同Ag含量的Ag-TiO 2催化剂。通过X射线衍射（XRD）、光致发光（PL）、表面光电压谱（SPS）、场诱导表面光电压谱（FISPS）和X射线光电子能谱（XPS）等表征手段，以及光催化降解罗丹明B（RhB）溶液的活性评价，发现Ag的掺杂促进了TiO 2的相变，同时也抑制了TiO 2微晶的生长。随着Ag掺杂量的增加，样品的PL和SPS强度均降低，表明Ag掺杂能有效抑制光生电子和空穴的复合。当Ag含量超过5mol%时，光生电子捕获活性位减少。在较低的Ag掺杂浓度下，Ag+离子的迁移和扩散占主导地位，而在较高的Ag掺杂浓度下，Ag+离子的迁移、扩散和还原同时发生。适当Ag含量（Ag物种浓度约为3 ~ 5mol%）的Ag-TiO 2光催化剂具有丰富的电子陷阱，有利于光生电子空穴对的分离，可大大提高光催化剂的活性。FISPS测试结果表明，Ag的同时掺杂和沉积在TiO 2的界面层中引入了杂质带和丰富的表面态，提高了TiO 2的可见光吸收能力。
Ag-TiO2 catalysts with different Ag contents were prepared via a sol-gel method in the absence of light. Based on the characterizations of XRD, photoluminescence (PL), surface photovoltage spectroscopy (SPS), field-induced surface photovoltage spectroscopy (FISPS), and XPS as well as the evaluation of the photocatalytic activity for degrading rhodamine B(RhB) solutions, it was found that the Ag dopant promoted the phase transformation as well as had an inhibition effect on the growth of anatase crystallite. The PL and SPS intensities were decreased with increasing Ag content, indicating that the Ag dopant could effectively inhibit the recombination of the photoinduced electrons and holes. However, the active sites capturing the photoinduced electrons reduced, while the Ag content exceeded 5 mol %. At rather low Ag dopant concentrations, the migration and diffusion of Ag+ ions were predominant, while at rather high Ag dopant concentrations, the migration, diffusion, and reduction of Ag ions simultaneously occurred. The Ag-TiO2 photocatalysts with appropriate content of Ag (Ag species concentration is from about 3 to 5 mol %) possessed abundant electron traps so as to be favorable for the separation of the photoinduced electron-hole pairs, which could greatly enhance the activity of the photocatalysts. From the results of FISPS measurements, it could be found that the impurity bands and abundant surface states were introduced into the interfacial layer of TiO2 because of Ag simultaneously doping and depositing, which could improve the absorption capability for visible light of the photocatalysts.